<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>练习1</title>
        <style>
            
        </style>
    </head>
    <body>
        body的内容
        <div id="one">
            div-one
            <div class="inside">div-one-inside</div>
        </div>
        <div id="two">
            div-two
            <div class="inside">div-two-inside</div>
        </div>
        <div id="three">
            div-three
            <div class="inside">div-three-inside</div>
        </div>
    </body>
</html>